Federal regulators are weighing whether to order an in-depth review of a utility's bid to reopen a damaged California nuclear plant.

The Nuclear Regulatory Commission yesterday left open the possibility of requiring a license amendment for the San Onofre Nuclear Generating Station, the Associated Press reported. The San Diego County plant has been shuttered since Jan. 31, when radiation escaped inside a steam generator.

It's "an open question" if a license amendment is necessary, NRC Regional Administrator Elmo Collins told the AP during a news conference in San Juan Capistrano. "I'm not saying yes or no."

Plant operator Southern California Edison Co. has filed paperwork seeking NRC's permission to restart one of two steam generators at San Onofre. The utility said that operating the Unit 2 equipment at 70 percent capacity will prevent the high-velocity flow of fluids that caused the generators to vibrate.

That led to wear on tubes carrying radioactive fluid. Degradation in Unit 3 allowed a small radiation leak, an investigation by NRC and Edison found.

Edison cannot restart without NRC's permission. A license amendment could take a year or more because it includes document submissions, hearings and potential appeals of the commission's ruling.

The decision is being watched closely by environmental groups, which argue that restarting the plant without an in-depth review puts Southern California at risk. More than 8 million people live within 50 miles of San Onofre. That distance is considered the evacuation zone should a major problem occur.

Edison "will not restart Unit 2 until the NRC states it is safe to do so," spokeswoman Jennifer Manfre said in an email.

"We have submitted our response to [NRC's confirmatory action letter] and restart plans," Manfre said. "SCE won't speculate on what the NRC would determine to be necessary in that evaluation."

Friends of the Earth and the Natural Resources Defense Council have formally requested a license amendment. NRDC plans to submit a letter to NRC tonight at a public meeting in Dana Point, Calif., that will argue reasons why the process is needed, said NRDC Western Director Joel Reynolds.

"A license amendment would permit an adjudicatory hearing in which Edison's claims would be tested via cross-examination and rebuttal by independent experts," said Dan Hirsch, president of the Committee to Bridge the Gap, an advocacy group. "In the absence of such a hearing there would be a closed-door deal to restart between Edison and NRC without full scrutiny of the risks."

Document disclosure

Edison has censored the public release of reports it has submitted to NRC in its request for a restart, Hirsch said. In an evidentiary hearing, all of those documents and others would be disclosed.

For example, he said, Edison's contention that it is safe to run Unit 2 at 70 percent capacity is based on a computer model. The utility in a hearing would have to submit all its computer runs, even those with unfavorable results.

"A safety determination should not be made based on claims that are being hid from scrutiny," Hirsch said.

Manfre said there was not censorship and that the documents Edison submitted to NRC were complete. Some of those prepared by Edison vendors were redacted to protect their proprietary information, she said, adding that "the redacted vendor information does not affect the substance of the Edison report or those vendors' conclusions."

The license amendment is needed because the damage to tubes in both units is extensive, Hirsch said. There are 1,595 worn tubes in Unit 2 and 1,806 in Unit 3.

Hirsch looked at the number of total locations where there was any damage on tubes and found it was 4,721 in Unit 2. He compared that to other nuclear plants across the country and found that the damage was more than 1,000 times greater than the median number of four for other facilities.

Edison has said the majority of the tube wall thinning "is not unusual in new steam generators and is part of the equipment settling in." The utility does not plan to repair Unit 2 before restarting it, arguing that it was less damaged than Unit 3 and has a superior support structure.

"They're going to turn the key on a device that's broken and keep their fingers crossed," Hirsch said. "That's why they don't want a hearing."

Environmental groups also have argued that San Onofre should have undergone a license amendment when it installed the generators as replacements in 2010 and 2011, because they were different from the earlier models.

Edison has said that it followed the appropriate process and regulation, which did not require a license amendment.

"The NRC has publicly stated that we followed the existing regulations," Manfre said.

Meeting with power plant's neighbors

NRC will meet tonight with residents to discuss San Onofre. But there is already conflict about the structure of the gathering.

The federal agency decided who would speak at the session, Hirsch said, and included several people who support nuclear. Hirsch said NRC rejected his request to speak or have NRDC's Reynolds talk during a round table in the first half of the event.

Hirsch called it likely a "dog-and-pony show," where nothing substantive would be discussed.

NRC's Collins has said that panelists were chosen in consultation with local interest groups.

"We want to provide members of the public with an opportunity to get their questions answered on a broad range of topics related to San Onofre," he said in announcing the session last month. "We think the round table discussion along with an open question-and-answer session will provide people with a means of doing this."

Panelists in the roundtable are: Rochelle Becker of the Alliance for Nuclear Responsibility; Ted Quinn of Californians for Safe and Clean Nuclear Energy; Gene Stone of Residents Organized for a Safe Environment; Donald Mosier, a physician at the Scripps Research Institute; Ken Schultz, a San Diego County resident; Richard McPherson, a Laguna Niguel, Calif., resident; and Grace Van Thillo, a San Clemente, Calif., resident.

Schultz and Quinn both are members of the American Nuclear Society, according to that group's website. It is an organization of "engineers and scientists devoted to the applications of nuclear science and technology."

Officials scheduled to be at the session will be NRC's Collins; Pete Dietrich, Edison's chief nuclear officer; Robert Oglesby of the California Energy Commission; and Ed Randolph of the California Public Utilities Commission.